Question

You measure the shadow cast by a certain tall building and find it to be 100  feet long. Then you measure the shadow cast by a 

three-foot  post and find it to be 4 inches  long. Determine the building's height.

Answer 1

First, set up a ratio:
`(1,200)/(x) = (4)/(36)`
The 1,200 in the first fraction is the length of the shadow in inches, and
`x` is the height of the building. The 4 is the length of the pole's shadow, and the 36 is it's height (both figures also in inches). Now divide the pole's height by it's shadow, and multiply that number by the building's shadow length:
`(1,200)/(10,800) = (4)/(36)`
This answer is in inches, so, divide the building's height by twelve to get the answer in feet:
`10,800 / 12 = 900` feet